/*
Copyright (c) 2014 - 2016 The Regents of the University of
California (Regents). All Rights Reserved.  Redistribution and use in
source and binary forms, with or without modification, are permitted
provided that the following conditions are met:
   * Redistributions of source code must retain the above
     copyright notice, this list of conditions and the following
     two paragraphs of disclaimer.
   * Redistributions in binary form must reproduce the above
     copyright notice, this list of conditions and the following
     two paragraphs of disclaimer in the documentation and/or other materials
     provided with the distribution.
   * Neither the name of the Regents nor the names of its contributors
     may be used to endorse or promote products derived from this
     software without specific prior written permission.
IN NO EVENT SHALL REGENTS BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
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ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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*/

package firrtl

import scala.collection.mutable.HashSet
import firrtl.ir._
import Mappers._

class Namespace private {
  private val tempNamePrefix: String = "GEN"
  // Begin with a tempNamePrefix in namespace so we always have a number suffix
  private val namespace = HashSet[String](tempNamePrefix)
  private var n = 0L

  def tryName(value: String): Boolean = {
    if (!namespace.contains(value)) {
      namespace += value
      true
    } else {
      false
    }
  }
  def newName(value: String): String = {
    var str = value
    while (!tryName(str)) {
      str = s"${value}_$n"
      n += 1
    }
    str
  }
  def newTemp: String = newName(tempNamePrefix)
}

object Namespace {
  // Initializes a namespace from a Module
  def apply(m: DefModule): Namespace = {
    val namespace = new Namespace

    def buildNamespaceStmt(s: Statement): Seq[String] = s match {
      case s: IsDeclaration => Seq(s.name)
      case s: Conditionally => buildNamespaceStmt(s.conseq) ++ buildNamespaceStmt(s.alt)
      case s: Block => s.stmts flatMap buildNamespaceStmt
      case _ => Nil
    }
    namespace.namespace ++= m.ports map (_.name)
    m match {
      case in: Module =>
        namespace.namespace ++= buildNamespaceStmt(in.body)
      case _ => // Do nothing
    }

    namespace
  }

  /** Initializes a [[Namespace]] for [[ir.Module]] names in a [[ir.Circuit]] */
  def apply(c: Circuit): Namespace = {
    val namespace = new Namespace
    namespace.namespace ++= c.modules map (_.name)
    namespace
  }

  /** Initializes a [[Namespace]] from arbitrary strings **/
  def apply(names: Seq[String] = Nil): Namespace = {
    val namespace = new Namespace
    namespace.namespace ++= names
    namespace
  }
}